title: Human baroreflex rhythms persist during handgrip and muscle ischaemia.
abstract: OBJECTIVE
  To determine whether physiological, rhythmic fluctuations of vagal baroreflex gain persist during exercise, post-exercise ischaemia and recovery.
  
  
  METHODS
  We studied responses of six supine healthy men and one woman to a stereotyped protocol comprising rest, handgrip exercise at 40% maximum capacity to exhaustion, post-exercise forearm ischaemia and recovery. We measured electrocardiographic R-R intervals, photoplethysmographic finger arterial pressures and peroneal nerve muscle sympathetic activity. We derived vagal baroreflex gains from a sliding (25-s window moved by 2-s steps) systolic pressure-R-R interval transfer function at 0.04-0.15 Hz.
  
  
  RESULTS
  Vagal baroreflex gain oscillated at low, nearly constant frequencies throughout the protocol (at approx. 0.06 Hz - a period of about 18 s); however, during exercise, most oscillations were at low-gain levels, and during ischaemia and recovery, most oscillations were at high-gain levels.
  
  
  CONCLUSIONS
  Vagal baroreflex rhythms are not abolished by exercise, and they are not overwhelmed after exercise during ischaemia and recovery.
authors.affiliation: Department of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Richmond, VA, USA; Medical College of Virginia at Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Eckberg
authors.forename: W H
authors.initials: WH
authors.lastname: Cooke
authors.forename: A
authors.initials: A
authors.lastname: Diedrich
authors.forename: B D
authors.initials: BD
authors.lastname: Levine
authors.forename: J A
authors.initials: JA
authors.lastname: Pawelczyk
authors.forename: J C
authors.initials: JC
authors.lastname: Buckey
authors.forename: A C
authors.initials: AC
authors.lastname: Ertl
authors.forename: I
authors.initials: I
authors.lastname: Biaggioni
authors.forename: J F
authors.initials: JF
authors.lastname: Cox
authors.forename: D
authors.initials: D
authors.lastname: Robertson
authors.forename: F J
authors.initials: FJ
authors.lastname: Baisch
authors.forename: C G
authors.initials: CG
authors.lastname: Blomqvist
authors.forename: T A
authors.initials: TA
authors.lastname: Kuusela
authors.forename: K U O
authors.initials: KU
authors.lastname: Tahvanainen
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D007511:Ischemia / Q000503:physiopathology; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*
keywords: exercise; resetting; sympathetic; vagal